Faced with aggressive deadlines to deliver specialized satellite parts, San Diego’s Vanguard Composites Group started a search. They needed to reduce the time required to machine thick composite sandwich panels before assembly. The large flat panels, made in a variety of measured thicknesses, serve as support structures for satellite antenna reflectors.

Vanguard is one of a group of specialized technology firms started under the incubator company, DR Technologies Inc. (DRT), a California C-Corporation. Founded in 1994, the company has been focused on composite hardware engineering and manufacturing since 2000.

Seeking to shorten set-up and production time, Vanguard’s Chief Machinist, Jim Branch, undertook a search for better tools and a process change. Among others, he considered a diamond coated carbide router, originally developed at AMAMCO Tool to solve a similar challenge within the Lockheed Martin F-35 joint strike fighter program.

After making further custom modifications specific to Vanguard’s needs, the tool, referred to as the compression router, successfully ended Branch’s search.

Eliminate Setup Time

Vanguard’s sandwich panels are composed of an aluminum honeycomb core that is covered on both sides by a thin composite skin that forms an extremely tough but lightweight building material. The resulting satellite antenna platforms and bases are manufactured for MDA of Canada, a key supplier of satellite missions for government and global commercial customers. MDA’s customer in this case is Gazprom Space Systems, one of Russia’s primary communications corporations.

Gazprom is preparing its latest Yamal 301 and 302 satellites for deployment over the Northern Euro-Asia continents as early as summer 2010, barring any production delays.

The two satellites will actually be joined into one unit, helping stretch its signal from the western most tip of Spain on the Atlantic all the way across the globe to the most Eastern points of Japan, in the Pacific.

Machining Composites

The original panel machining process was accomplished in three labor-intensive steps. Two separate set-ups were required to machine both composite skin edges around each panel. Then, the trimming of the core aluminum material required yet a third set-up.

As expected, AMAMCO’s diamond coated compression router significantly improved the edge quality of the composite skin by eliminating break out or backside delamination (the splitting apart of composite layers – see the Lockheed case history that follows). The router produced a clean, finished edge – more than any previously used tool.

Process Change

A custom solution to modifying the compression router, to accommodate a process change was advised. Modest tool sizing gave machinists the ability to trim the aluminum honeycomb core material and both composite skins, all in a single one-up process that eliminated scrap to nil, further reducing total production time and cost. The change reduced machine time from six to three days, on average. The total shop-day savings per application averaged 14 days.

Once it was recognized that Vanguard’s application involved similar material and set-up requirements to the Lockheed F-35’s wing skin process, Vanguard felt strongly that AMAMCO’s compression router offered both the tool and the process needed.

Data Reveals Cost Savings

Testing results documented during the Lockheed F-35 wing fabrication process convinced Vanguard that the compression router deserved serious consideration. The data revealed significant improvement in the condition of the aircraft’s composite wing skin edges and increased manufacturing efficiencies. The data clearly showed superior performance of coated carbide over the more costly PCD tool that was originally specified.

Testing was conducted by the National Center for Defense Manufacturing and Machining (NCDMM), which studied the entire process to develop a proven best practice process.

One of the investigations NCDMM carried out was a thorough analysis of tool cutting geometries within application parameters that revealed valuable information about the effects of cutting forces.

During testing, AMAMCO was able to develop surface tool geometries that vastly increased cutting efficiency and tool life. And, equally important, the testing revealed that a coating process could protect those geometries, vastly extending the tool’s life. The coating process, provided by Diamond Tool Coating is chemical vapor deposition (CVD), which produces a multilayered diamond coating.

The router’s opposing cutting forces, which cause simultaneous up and down cuts, cleanly and quickly removed material making it an efficient choice for trimming and shaping composites. Instead of the smearing effect that resulted with the straight or slightly angled flute of the PCD tool, the compression router utilizes the advantages of the helical flute and counter cutting forces to cleanly shear the composite fibers, eliminating delamination (separation of composite layers).

Data showed PCD tool failure after only nine linear feet, while causing excessive delamination. By contrast, the AMAMCO diamond coated compression router lasted more than six times longer, or 57 linear feet and caused no delamination. Tested material sections, ultrasonically inspected by Lockheed, verified the integrity of the parts and the absence of delamination.

After applying a process change, Lockheed fabricators could machine a complete wingskin using only two compression routers – one to rough and one to finish – instead of the 24 PCD cutting tools, previously required. The thorough performance analysis revealed achieved savings: While on a much smaller scale, practical results at Vanguard revealed the same pattern of reduced tool cost and faster production times.

Launcher Proton-K with Yamal-200 Satellites at the Launch pad. Baikonur, November 20, 2003.

Satellite hardware engineering and manufacturing personnel at Vanguard Composites were some of the earliest enthusiasts to work with composites. Decades ago they faced the challenge of launching very high performance components into space, but were allowed only relatively lightweight payloads. Until recently, these specialized component parts had to be handmade at great expense to achieve performance levels that today are being reached by using lightweight and tough composites.

Vanguard and other manufacturers are now benefiting from custom tools developed specifically for machining composites from within the U.S. aerospace industry.